Inhibition of dipeptidyl peptidase-IV (DPP-IV), an enzyme that inactivates both glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide 1 (GLP-1), represents a novel approach to the treatment and prevention of Type 2 diabetes, also known as non-insulin dependent diabetes mellitus (NIDDM). The therapeutic potential of DPP-IV inhibitors for the treatment of Type 2 diabetes has been reviewed: C. F. Deacon and J. J. Holst, “Dipeptidyl peptidase IV inhibition as an approach to the treatment and prevention of Type 2 diabetes: a historical perspective,” Biochem. Biophys. Res. Commun., 294: 1-4 (2000); K. Augustyns, et al., “Dipeptidyl peptidase IV inhibitors as new therapeutic agents for the treatment of Type 2 diabetes,” Exp. Opin. Ther. Patents, 13: 499-510 (2003); D. J. Drucker, “Therapeutic potential of dipeptidyl peptidase IV inhibitors for the treatment of Type 2 diabetes,” Exp. Opin. Investig. Drugs, 12: 87-100 (2003); and C. F. Deacon, et al., “Inhibitors of dipeptidyl peptidase IV: a novel approach for the prevention and treatment of Type 2 diabetes,” Exp. Opin. Investig. Drugs, 13: 1091-1102 (2004).
U.S. Pat. No. 6,699,871 (issued Mar. 2, 2004), the contents of which are incorporated by reference herein in their entirety, describes a class of beta-amino tetrahydrotriazolo[4,3-α]pyrazines, which are potent inhibitors of DPP-IV useful for the treatment of Type 2 diabetes. Specifically disclosed in this U.S. patent is (2R)-4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-α]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine. However, there is no disclosure of the newly discovered amorphous form of the dihydrogenphosphate salt of (2R)-4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-α]pyrazin-7(8H)-yl]-1-(2,4,5-triflourophenyl)butan-2-amine of structural formula I below (hereinafter referred to as Compound I).